Multi-layer cyclic redundancy check code in wireless communication system

ABSTRACT

A wireless communication device including a first CRC coder that generates a first block of CRC parity bits on a transport block and associates the first block of CRC parity bits with the transport block, a segmenting entity that segments the transport block into multiple code blocks after associating, and a second coder that generates a second block of CRC parity bits on each code block and associates a second block of CRC parity bits with each code block. The first and second blocks of CRC parity bits are based on first and second generator polynomials.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications, andmore specifically to the coding of data using cyclic redundancy check(CRC) codes.

BACKGROUND

CRC coding is commonly used to detect errors in data transmitted inwireless communication systems. In the evolving 3GPP LTE specification,for example, it has been proposed that 24 CRC parity bits be generatedbased on the entire transport block (TB). The 24 CRC parity bits arethen attached to the TB, after which the TB is segmented into multiplecode blocks (CBs). In the LTE proposal, 24 CRC parity bits are alsocalculated based on each code block (CB) and the 24 CRC parity bits arethen attached to the corresponding CB. In the LTE proposal, the samegenerator polynomial is used in the generation of the CRC parity bitsbased on the transport block and in the generation of the CRC paritybits based on the code blocks. The first transport CRC encoding helpsthe receiving device to detect residual errors. It has been suggestedthat the CRC encoding of the code blocks may be used by the receivingdevice to reduce the number of turbo decoding processes, or to reducethe number of turbo decoding iterations, or to reduce turbo decodermemory usage. The code blocks are then channel encoded, for example,with a turbo code, prior to transmission.

The various aspects, features and advantages of the disclosure willbecome more fully apparent to those having ordinary skill in the artupon careful consideration of the following Detailed Description thereofwith the accompanying drawings described below. The drawings may havebeen simplified for clarity and are not necessarily drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system.

FIG. 2 is a schematic block diagram of a wireless communication deviceincluding a transmitter.

FIG. 3 is a schematic block diagram of a wireless communication deviceincluding a receiver.

DETAILED DESCRIPTION

In FIG. 1, the wireless communication system 100 includes one or morefixed base infrastructure units forming a network distributed over ageographical region. A base unit may also be referred to as an accesspoint, access terminal, Node-B, eNode-B, or by other terminology used inthe art. The one or more base units 101 and 102 serve a number of remoteunits 103 and 110 within a serving area, for example, a cell, or withina cell sector. The remote units may be fixed units or mobile terminals.The remote units may also be referred to as subscriber units, mobilestations, users, terminals, subscriber stations, user equipment (UE),terminals, or by other terminology used in the art.

Generally, base units 101 and 102 transmit downlink communicationsignals 104 and 105 to serving remote units in the time and/or frequencydomain. Remote units 103 and 110 communicate with one or more base units101 and 102 via uplink communication signals 106 and 113. The one ormore base units may comprise one or more transmitters and one or morereceivers that serve the remote units. The remote units may alsocomprise one or more transmitters and one or more receivers.

In one embodiment, the communication system utilizes OFDMA or a nextgeneration single-carrier (SC) based FDMA architecture for uplinktransmissions, such as interleaved FDMA (IFDMA), Localized FDMA (LFDMA),DFT-spread OFDM (DFT-SOFDM) with IFDMA or LFDMA. In OFDM based systems,the radio resources include OFDM symbols, which may be divided intoslots, which are groupings of sub-carriers. An exemplary OFDM basedprotocol is the developing 3GPP LTE protocol.

Error detection is provided on protocol data units, for example,transport blocks, through a Cyclic Redundancy Check (CRC). FIG. 2 is awireless communication device 200, or portion thereof, configured to CRCcode data for transmission in a wireless communication system. In FIG. 1such data is transmitted between the base station 101 and the remoteunit 103. In 3GPP LTE implementations, the data or protocol data unit isa transport block. CRC coding generally occurs in the transmitter ofboth the base unit and the remote unit. In FIG. 2, the transmitterincludes a first CRC coder entity 210 configured to generate a firstblock of CRC parity bits on a transport block 202.

The entire transport block is generally used to calculate or generatethe CRC parity bits. Denote the bits in a transport block delivered tolayer 1 by a₀, a₁, a₂, a₃, . . . , a_(A−1), and the parity bits by p₀,p₁, p₂, p₃, . . . , p_(L−1). A is the size of the transport block and Lis the number of parity bits. In one 3GPP LTE implementation, the firstblock includes 24 CRC parity bits, i.e., L set to 24 bits, although moregenerally, the block may include some other number of parity bits. Theparity bits are computed based on a first CRC generator polynomial 212.The first block of CRC parity bits are generally associated with thetransport block. In FIG. 2, the first block of CRC parity bits 204 areappended to the transport block 202. In other embodiments, the firstblock of CRC parity bits are attached to some other portion of thetransport block.

In FIG. 2, the wireless communication device 200 also includes asegmentation entity 214. The transport block with the first CRC paritybits attached are delivered to the segmentation entity. The input bitsequence to the code block segmentation is denoted by b₀, b₁, b₂, b₃, .. . , b_(B−1), where B>0. The segmentation entity segments the transportblock 202 having the associated first block of CRC parity bits into aplurality of code blocks 206, 207, 208. A second CRC coder entity 216 isconfigured to generate a second block of CRC parity bits on each of theplurality of code blocks 206, 207 and 208. Each of the second blocks ofCRC parity bits are based on a second generator polynomial 218. In one3GPP LTE implementation, the second block of CRC parity bits alsoincludes 24 CRC parity bits. Each of the second blocks of CRC paritybits is then associated with the corresponding code block on which thesecond block of CRC parity bits is based. In FIG. 2, the second blocksof CRC parity bits 230, 232 and 234 are appended to the correspondingcode blocks 206, 207 and 208. This process may be implemented seriallyfor each of the segmented code blocks. In some implementations,segmentation is conditional. For example, if B is larger than themaximum code block size, e.g., Z=6144, segmentation of the input bitsequence is performed and an additional CRC sequence of L=24 bits isattached to each code block where the CRC bits are calculated based on asecond CRC generator polynomial. If B is smaller than or equal to themaximum code block size, then code block segmentation 214 istransparent, and no second block of CRC parity bits are needed.

The inventors have recognized that the use of the same generatorpolynomials for the first and second CRC coders 210 and 216 in FIG. 2leads to error events that remain undetected at one or both levels ofCRC checking. If the error event remains undetected at both levels ofCRC checking, the receiver will accept an incorrect block as a correctone. Therefore, it is preferable to reduce the error events that mayremain undetected at both levels of CRC checking. For a CRC code, anerror event that is equal to a non-zero codeword cannot be detected bythe CRC decoder. It is also noted that a non-cyclic shifted version of acodeword is still a codeword. Therefore, when the same generatorpolynomials for the first and second CRC coders are chosen, anundetectable error event in the systematic portion of the code blockwill remain undetected at both levels of CRC checking and the receivermay accept an incorrect block.

The inventors have recognized further that the error detectioncapability of the two-level CRC can be improved by using differentgenerator polynomials for CRC encoding the transport block and thesegmented code blocks. Thus in some embodiments, the first and secondgenerator polynomials are different. In one embodiment, for example, thefirst and second generator polynomials have at least one differentfactor. In another embodiment, the first and second generatorpolynomials share no common factors. In another embodiment, the firstand second generator polynomials have different sets of polynomialcoefficients. In other embodiments, the first and second generatorpolynomials are distinguished by other characteristics. More generally,the first and second polynomials may be distinguished by a combinationof these and/or other characteristics. In one embodiment, the first andsecond generator polynomials share a factor of (D+1) and/or a commondegree. In other embodiments, however, the first and second generatorpolynomials are the same as discussed further below.

In one implementation, the first and second degree generator polynomialsare selected from a group comprising the following degree-24 CRCgenerator polynomials sharing at most a factor of (D+1):

-   -   g_(CRC24,a)(D)=D²⁴+D²³+D⁶+D⁵+D+1. This generator polynomial can        be factored into the following form: (D+1)(D²³+D⁵+1);    -   g_(CRC24,b)(D)=D²⁴+D²¹+D²⁰+D¹⁷+D¹⁵+D¹¹+D⁹+D⁸+D⁶+D⁵+D+1. This        generator polynomial can be factored into the following form:        g _(CRC24,b)(D)=(D+1)(D ²³ +D ²² +D ²¹ +D ¹⁹ +D ¹⁸ +D ¹⁷ +D ¹⁴        +D ¹³ +D ¹² +D ¹¹ +D ⁸ +D ⁵+1);    -   g_(CRC24,c)(D)=D²⁴+D²³+D¹⁸+D¹⁷+D¹⁴+D¹¹+D¹⁰+D⁷+D⁶+D⁵+D⁴+D³+D+1.        This generator polynomial can be factored into the following        form: (D+1)(D²³+D¹⁷+D¹³+D¹²+D¹¹+D⁹+D⁸+D⁷+D⁵+D³+1);    -   g_(CRC24,d)(D)=D²⁴+D²³+D¹⁴+D¹²+D⁸+1. This generator polynomial        can be factored into the following form:=(D+1) (D³+D²+1)        (D¹⁰+D⁸+D⁷+D⁶+D⁵+D⁴+D³+D+1)(D¹⁰+D⁹+D⁴+1);        g _(CRC24,e)(D)=D ²⁴ +D ²¹ +D ²⁰ +D ¹⁶ +D ¹⁵ +D ¹⁴ +D ¹³ +D ¹²        +D ¹¹ +D ¹⁰ +D ⁹ +D ⁸ +D ⁴ +D ³+1;    -   g_(CRC24,f)(D)=D²⁴+D²²+D²⁰+D¹⁹+D¹⁸+D¹⁶+D¹⁴+D¹³+D¹¹+D¹⁰+D⁸+D⁷+D⁶+D³+D+1.        This generator polynomial can be factored into the following        form: (D+1)²(D¹¹+D⁹+D⁸+D⁷+D⁶+D³+1) (D¹¹+D⁹+D⁸+D⁷+D⁵+D³+D²+D+1);    -   g_(CRC24,g)(D)=D²⁴+D²²+D²¹+D²⁰+D¹⁹+D¹⁷+D¹⁶+D⁸+D⁷+D⁵+D⁴+D³+D²+1.        This generator polynomial can be factored into the following        form:        (D+1)²(D ²² +D ¹⁹ +D ¹⁸ +D ¹⁶ +D ¹⁵ +D ¹³ +D ¹¹ +D ⁹ +D ⁷ +D ⁶        +D ⁴ +D ³+1);    -   g_(CRC24,h)(D)=D²⁴+D²¹+D²⁰+D¹⁷+D¹³+D¹²+D³+1. This generator        polynomial can be factored into the following form:        (D+1)²(D ¹¹ +D ¹⁰ +D ⁹ +D ⁸ +D ⁷ +D ⁶ +D ⁵ +D ²+1) (D ¹¹ +D ¹⁰        +D ⁹ +D ⁷ +D ⁶ +D ⁵ +D ⁴ +D ³+1);    -   g_(CRC24,i)(D)=D²⁴+D²²+D¹²+D¹⁰+D⁹+D²+D+1). This generator        polynomial can be factored into the following form:        (D+1)²(D¹¹+D⁹+1)(D¹¹+D⁹+D⁷+D⁵+D³+D+1); and    -   g_(CRC24,j)(D)=D²⁴+D²²+D²⁰+D¹⁹+D¹⁷+D¹⁶+D¹⁵+D¹⁴+D¹⁰+D⁷+D⁶+D⁵+D⁴+D²+1.        This generator polynomial can be factored into the following        form: (D¹²+D¹¹+D⁷+D⁴+D²+D+1) (D¹²+D¹¹+D⁸+D⁷+D⁵+D⁴+D²+D+1).

In another implementation, the first and second degree generatorpolynomials are selected from a group comprising one of the abovedegree-24 CRC generator polynomials and the reciprocal of one of theabove degree-24 CRC generator polynomials. The reciprocal polynomialg(D) of degree n−k is D^(n−k)g(D⁻¹). For example, the reciprocal ofg_(CRC24a)(D) is 1+D+D¹⁸+D¹⁹+D²³+D²⁴=(D+1)(D²³+D¹⁸+1). In a moreparticular implementation, the first and second degree generatorpolynomials are selected from the group of g_(CRC24a)(D) and thereciprocal of g_(CRC24a)(D).

In another implementation, the first and second generator polynomialsare selected from a group of generator polynomials comprising:D²⁴+D²³+D⁶+D⁵+D+1; D²⁴+D²¹+D²⁰+D¹⁷+D¹⁵+D¹¹+D⁹+D⁸+D⁶+D⁵+D+1; andD²⁴+D²³+D¹⁸+D¹⁷+D¹⁴+D¹¹+D¹⁰+D⁷+D⁶+D⁵+D⁴+D³+D+1. In anotherimplementation, at least one of the first and second generatorpolynomials is D²⁴+D²³+D⁶+D⁵+D+1.

An L-bit CRC coder may be implemented using polynomial arithmetic asfollows. In the CRC calculation, denote the input bits to the CRCcomputation by a₀, a₁, a₂, a₃, . . . , a_(A−1) and the parity bits byp₀, p₁, p₂, p₃, . . . , p_(L−1). A is the size of the input sequence andL is the number of parity bits. The parity bits are generated by acyclic generator polynomials or CRC generator polynomials (g_(CRC)(D))with L CRC parity bits. The encoding is performed in a systematic form,which means that in GF(2), the polynomial:a ₀ D ^(A+L−1) +a ₁ D ^(A+L−2) + . . . +a _(A−1) D ^(L) +p ₀ D ^(L−1) +p₁ D ^(L−2) + . . . +p _(L−2) D+p _(L−1)

This polynomial yields a remainder equal to 0 when divided byg_(CRC)(D). The bits after CRC attachment are denoted by b₀, b₁, b₂, b₃,. . . , b_(B−1), where B=A+L. The relation between a_(k) and b_(k) is:b _(k) =a _(k) for k=0, 1, 2, . . . , A−1b _(k) =p _((L−1−(k−A))) for k=A, A+1, A+2, . . . , A+L−1.

In another approach, the relation between a_(k) and b_(k) can befollows:b _(k) =a _(k) for k=0, 1, 2, . . . , A−1b _(k) =p _((k−A)) for k=A, A+1, A+2, . . . , A+L−1.

In FIG. 2, the wireless communication device 200 also includes a channelencoding entity 222 configured to encode each of the code blocksincluding the associated second block of CRC parity bits. The channelencoding entity may embody any number of different forms including butnot limited to a turbo encoder or a convolutional encoder among otherchannel encoders. The transmitter also includes a concatenating entity224 configured to concatenate the code blocks after channel encoding.The output of the concatenating entity is coupled to a power amplifierfor transmission. The concatenating entity 224 may perform a series ofone or more other operations to prepare the code blocks fortransmission, for example, rate matching, HARQ redundancy versionselection, channel interleaving, bit scrambling, mapping to physicalchannel resources, bit-to-symbol mapping, IFFT, DFT spreading, etc.

FIG. 3 is a wireless communication device 300, or portion thereof,configured to receive and decode data encoded with a CRC code. Thedevice 300 receives code blocks 206, 207 and 208 each of which isassociated with a corresponding block of CRC parity bits 230, 232, and234, respectively. These CRC coded code blocks correspond to the codeblocks transmitted by the transmitter 200 of FIG. 2. The device 300includes a CRC removal entity 310 configured to disassociate the secondblock of CRC parity bits associated with each of a plurality of receivedcode blocks, thus leaving the code block 206, 207 and 208. The removalof the second block of CRC parity bit is based on a second CRC generatorpolynomial 312. The function performed by the CRC removal entity in FIG.3 essentially reverses the process performed by the second CRC coderentity 216 in FIG. 2. Thus the second CRC generator polynomial 312 usedby the CRC removal entity 310 in FIG. 3 is the same as the second CRCgenerator polynomial 218 used by the second CRC coder entity 216 togenerate and associate the second block of CRC parity bits with the codeblocks in FIG. 2.

In FIG. 3, the device 300 includes a concatenator entity 314 configuredto form an estimated transport block 205 having a first block of CRCparity bits 204 associated therewith. The concatenator entity 314concatenates the code blocks 206, 207 and 208 after the associatedsecond block of CRC parity bits are removed by the CRC removal entity310. The concatenator entity 314 of FIG. 3 essentially reverses theprocess performed by the segmentation entity 214 of FIG. 2. Thus in FIG.3 the first block of CRC parity bits 204 corresponds substantially tothe first block of CRC parity bits 204 associated with the transportblock 202 in FIG. 2.

In FIG. 3, the device 300 includes a CRC decoder entity 316 configuredto perform a CRC check on the estimated transport block 202 based on afirst generator polynomial 318. As noted, the first generator polynomial318 in FIG. 3 corresponds to the first generator polynomial 212 in FIG.2. The CRC check determines whether the estimated transport block 205recovered by the receiver corresponds to the transmitted transportblock, for example, the transport block 202 in FIG. 2. Upon detectingerror by the CRC check, the estimated transport block is taken as notcorresponding to the transmitted transport block, and a retransmissionmay be requested. If no errors are detected, the estimated transportblock is taken as corresponding to the transmitted transport block anddelivered to higher layers. It is known generally that CRC checks have acertain probability of undetected error, which is a measurement of theperformance of the CRC code.

In some embodiments, the device 300 includes a second CRC decoder entity320 configured to perform a CRC check on the plurality of code blocks206, 207 and 208 received at the receiver. The CRC decoder entity 320performs a check on the code blocks before the code blocks areconcatenated to form the estimated transport block and thus before theperformance of the CRC check on the estimated transport block 205. Insome embodiments, the first block of CRC parity bits associated with theestimated transport block 205 is based on a first generator polynomial318 that is different than the second generator polynomial 312 formingthe basis of the second block of CRC parity bits associated with thecode blocks. In other embodiments, however, the first and secondgenerator polynomials are the same as discussed further below. In someembodiments, the CRC encoding of the code blocks may be used by thereceiving device to reduce the number of turbo decoding processes, or toreduce the number of turbo decoding iterations, or to reduce turbodecoder memory usage.

In some embodiments including the second CRC decoder entity 320, the CRCcheck performed on the estimated transport block 205 is conditional. Inone implementation, the CRC check is performed on the estimatedtransport block 205 only if the CRC checks performed on the plurality ofcode blocks 206, 207 and 208 do not detect any errors. In FIG. 3, aconditional controller 322 provides a signal that controls whether theCRC decoder 316 performs a CRC check on the estimated transport block205 based on whether errors have been detected on the code blocks 206,207 and 208. In some implementations, the code blocks are re-transmittedif errors are detected on the code blocks by the second CRC decoderentity 320. In some implementations, the transport block isretransmitted if errors are detected.

In an alternative embodiment of FIG. 2, the first and second generatorpolynomials 212 and 218 used to generate the first and second blocks ofCRC parity bits share at least one factor. In one implementation, thefirst and second generator polynomials are the same. In this alternativeembodiment, an interleaving operation is perform in the transport block202 after associating the first block of CRC parity bits. Interleavingis performed by an interleaver entity 240. In one embodiment, theinterleaving is performed before segmentation and thus the interleaverentity 240 is located between the first CRC coding entity and thesegmentation entity. In an alternative embodiment, the interleaving isperformed after segmentation but before CRC encoding of the code blocks.In this alternative embodiment, the interleaving entity 240 is locatedbetween the segmentation entity and the second CRC encoding entity 216.The interleaving pattern may be defined in a manner such thatinterleaving the transport block 202 after associating the first blockof CRC parity bits 204 and segmenting the interleaved transport blockinto multiple code blocks is equivalent to segmenting the transportblock 202 into multiple code blocks after associating the first block ofCRC parity bits and interleaving the code blocks 206, 207 and 208individually. This equivalency may be conceptual where interleaving isperformed before segmenting. Alternatively, the equivalency may bephysical where the interleaver is realized by performing a plurality ofsub-interleaving after segmenting. In one implementation, interleavingof the transport block 202 is performed at bit level. In anotherimplementation, interleaving the transport block is performed bypermuting groups wherein each group contains a plurality of bits.

In some implementations, the interleaver permutation in FIG. 2 maydisallow the same undetectable error event being kept between thefirst-level CRC check and the second-level CRC check, thus leading toimproved error detection properties. While interleaving is one choice,additional transformations beyond re-ordering (or interleaving) thatwould disallow the same undetectable error being kept betweenfirst-level CRC check and second-level CRC check may also be viable. Theinterleaving introduced between the transport block and the code blocksmay interleave one bit or one byte (or groups of bits of other size) ata time. If the interleaving is performed at the transport block level,one interleaver associated with the transport block after associatingthe first block of CRC parity bits is needed. Alternatively, theinterleaving may be performed at the code block level (i.e.,interleaving wherein bits for different segments are not mixed). Forcode block level interleaving, a total of C sub-interleavers may beneeded, where C is the number of message segments. The i-thsub-interleaver is associated with the i-th code block. Theinterleavers, at the transport block level or the code block level, maybe of a simple format such as reversal, i.e., reading bits from end tofront, cyclic shifting, bit-reversal, etc. It is possible thatinterleaving may require additional latency or circuitry at the receiverthough the exact amount can be reduced by choosing the interleaverssuitably.

In FIG. 3, in implementations where the first and second generatorpolynomials are the same and the transport block or code block areinterleaved by the transmitting device, the receiving device includes adeinterleaver entity 328. If interleaving occurs on the transport blockin the transmitting device, the deinterleaving entity 328 is locatedafter the concatenating entity 314 in the receiver device as illustratedin FIG. 3. If interleaving occurs on the code blocks in the transmittingdevice, the deinterleaving entity is located before the concatenatingentity in the receiver device.

Compared to using the same generator polynomial in the first and thesecond CRC coder without interleaving, more circuitry and/or memory aregenerally required to implement using different generator polynomialsfor the first and the second CRC coders and also to implementinterleaving after associating the first block of CRC bits to thetransport block. However, the cost associated with the increasedcomplexity is likely outweighed by the enhanced performance of the errordetection.

While the present disclosure and the best modes thereof have beendescribed in a manner establishing possession and enabling those ofordinary skill to make and use the same, it will be understood andappreciated that there are equivalents to the exemplary embodimentsdisclosed herein and that modifications and variations may be madethereto without departing from the scope and spirit of the inventions,which are to be limited not by the exemplary embodiments but by theappended claims.

1. A wireless communication device comprising: a first cyclic redundancycheck CRC coder configured to generate a first block of CRC parity bitson a transport block, the first block of CRC parity bits based on afirst generator polynomial, the first CRC coder associating the firstblock of CRC parity bits with the transport block; a segmenting entityhaving an input coupled to the first CRC coder, the segmenting entityconfigured to segment the transport block into multiple code blocksafter associating; a second CRC coder configured to generate a secondblock of CRC parity bits on each code block, each of the second block ofCRC parity bits are based on a second generator polynomial, the secondCRC coder associating a second block of CRC parity bits with each codeblock, the second block of CRC parity bits associated with each codeblock is the second block of CRC parity bits generated based on thecorresponding code block; the second generator polynomial is differentthan the first generator polynomial; a channel encoder configured toencode each of the code blocks including the associated second block ofCRC parity bits.
 2. The device of claim 1, wherein the first and secondgenerator polynomials having a common degree.
 3. The device of claim 1,wherein the first and second generator polynomials have at least onedifferent factor.
 4. The device of claim 3, wherein the first and secondgenerator polynomials share no factors.
 5. The device of claim 3,wherein the first and second generator polynomials share a factor of(D+1).
 6. The device of claim 1, the first and second generatorpolynomials having different sets of polynomial coefficients.
 7. Thedevice of claim 1, selecting the first and second generator polynomialsfrom a group of generator polynomials comprising: D²⁴+D²³+D⁶+D⁵+D+1;D²⁴+D²¹+D²⁰+D¹⁷+D¹⁵+D¹¹+D⁹+D⁸+D⁶+D⁵+D+1; andD²⁴+D²³+D¹⁸+D¹⁷+D¹⁴+D¹¹+D¹⁰+D⁷+D⁶+D⁵+D⁴+D³+D+1.
 8. The device of claim1, wherein the first generator polynomial is D²⁴+D²³+D⁶+D⁵+D+1.
 9. Thedevice of claim 1, wherein the second generator polynomial isD²⁴+D²³+D⁶+D⁵+D+1.
 10. A method in a wireless communication transmitter,the method comprising: generating, at the transmitter, a first block offirst cyclic redundancy check CRC parity bits on a transport block, thefirst block of CRC parity bits based on a first generator polynomial;associating the first block of CRC parity bits with the transport block;segmenting the transport block into multiple code blocks afterassociating; generating, at the transmitter, a second block of CRCparity bits on each code block, each of the second block of CRC paritybits based on a second generator polynomial, the second generatorpolynomial is different than the first generator polynomial; associatinga second block of CRC parity bits with each code block, the second blockof CRC parity bits associated with each code block is the second blockof CRC parity bits generated based on the corresponding code block;channel encoding, at the transmitter, each of the code blocks includingthe associated second block of CRC parity bits; concatenating the codeblocks after channel encoding.
 11. A method in a wireless communicationreceiver, the method comprising: disassociating, at the receiver, asecond block of cyclic redundancy check CRC parity bits associated witheach of a plurality of received code blocks, the second block of CRCparity bits are generated based on a second generator polynomial andbased on the corresponding code block with which the second block of CRCparity bits are associated; forming, at the receiver, an estimatedtransport block having a first block of CRC parity bits associated withthe estimated transport block by concatenating the code blocks afterremoving the associated second block of CRC parity bits, wherein thefirst block of CRC parity bits associated with the transport block isbased on a first generator polynomial that is different than the secondgenerator polynomial, performing, at the receiver, a CRC check on theestimated transport block based on the first generator polynomial. 12.The method of claim 11, wherein a CRC check is performed on theplurality of code blocks before performing the CRC check on theestimated transport block.
 13. The method of claim 12, wherein the CRCcheck on the estimated transport block is performed only if the CRCcheck on the plurality of code blocks does not detect any errors.
 14. Amethod in a wireless communication transmitter, the method comprising:generating, at the transmitter, a first block of cyclic redundancy checkCRC parity bits on a transport block, the first block of CRC parity bitsgenerated based on a generator polynomial; associating the first blockof CRC parity bits with the transport block; interleaving the transportblock after associating; segmenting the interleaved transport block intomultiple code blocks; generating, at the transmitter, a second block ofCRC parity bits on each code block, each of the second block of CRCparity bits are generated based on the generator polynomial; associatinga second block of CRC parity bits with each code block, the second blockof CRC parity bits associated with each code block is the second blockof CRC parity bits generated based on the corresponding code block;channel encoding, at the transmitter, each of the code blocks includingthe associated second block of CRC parity bits; concatenating the codeblocks after channel encoding.
 15. The method of claim 14, whereininterleaving the transport block is performed at bit level.
 16. Themethod of claim 14, wherein interleaving the transport block isperformed by permuting groups wherein each group contains a plurality ofbits.
 17. The method of claim 14, wherein interleaving the transportblock after associating the first block of CRC parity bits andsegmenting the interleaved transport block into multiple code blocksafter associating the first block of CRC parity bits is equivalent tosegmenting the transport block into multiple code blocks afterassociating the first block of CRC parity bits and interleaving the codeblocks individually.